The present invention relates to metal panels having a system of internal tubular passageways disposed between spaced apart portions of the thickness of the panel. Said panels possess utility in heat exchange applications wherein a heat exchange medium is circulated through said passageways. A particular application of said panels resides in devices utilizing solar energy, and specifically, solar energy absorbing devices for elevating fluid temperature.
It is well known that the radiation of the sun can be collected as a source of energy for heating or cooling or for direct conversion to electricity. Heating and cooling depend upon collection of rays of solar energy in a fluid heating transfer system. The heated fluid is pumped or allowed to flow to a place of utilization for the thermal energy it has acquired.
In certain areas of the world, solar energy is the most abundant form of available energy if it could be harnessed economically. Even in more developed areas of the world, the economic harnessing of solar energy would provide an attractive alternative to the use of fossil fuels for energy generation.
One of the problems attending the development of an efficient system for the conversion of solar energy resides with the structure and design of the solar energy absorbing device, or solar collector. This solar collector generally comprises a rectangular plate-like structure possessing channels or passageways for the circulation of the energy absorbing fluid medium. Conventionally, these panels have comprised a pair of opposed expanded passageways, known as headers, which are placed at opposite ends of the panel, and are connected by a plurality of tubular passageways which are often in parallel relation with respect to each other. These passageways, as well as the headers themselves, have generally been disposed at right angles with respect to each other and in parallel relation with respect to the horizontal and vertical dimensions, respectively, of the panel.
The aforementioned configuration suffers from certain deficiencies, in that fluid flow tends to encounter pockets of stagnation which cut down on the efficient circulation of solar energy. Further, various entrained gases tend to collect in the passageways, with the result that air locks which greatly inhibit flow and reduce the maximum fluid circulation capacity of the panel are often formed.
In our co-pending application Ser. No. 573,953, the disclosure of which is incorporated herein by reference, it was determined that improved flow was obtainable by a modification of the disposition of the headers wherein the headers define an angle of at least 91.degree. with respect to the direction of flow of the heat exchange medium. Though this modification alleviates the aforenoted problems to an extent, it was felt that further improvement in flow was desirable in certain of the panel configurations. To this end the improvements embodied in the present invention were developed.